Source : Webster's Revised Unabridged Dictionary (1913)

Nonpareil \Non`pa*reil"\, n. [See {Nonpareil}, a. ]
   1. Something of unequaled excellence; a peerless thing or
      person; a nonesuch; -- often used as a name.

   2. [F. nonpareille.] (Print.) A size of type next smaller
      than minion and next larger than agate (or ruby).

   Note: This line is printed in the type called nonpareil.

   3. (Zo["o]l.)
      (a) A beautifully colored finch ({Passerina ciris}),
          native of the Southern United States. The male has the
          head and neck deep blue, rump and under parts bright
          red, back and wings golden green, and the tail bluish
          purple. Called also {painted finch}.
      (b) Any other similar bird of the same genus.

Nonpareil \Non`pa*reil"\, a. [F., from non not + pareil equal,
   fr. LL. pariculus, dim. of L. par equal. See {Non}, and
   {Pair}, {Peer}.]
   Having no equal; peerless.

Source : WordNet®

nonpareil
     adj : eminent beyond or above comparison; "matchless beauty"; "the
           team's nonpareil center fielder"; "she's one girl in a
           million"; "the one and only Muhammad Ali"; "a peerless
           scholar"; "infamy unmatched in the Western world";
           "wrote with unmatchable clarity"; "unrivaled mastery of
           her art" [syn: {matchless}, {one(a)}, {one and only(a)},
            {peerless}, {unmatched}, {unmatchable}, {unrivaled}, {unrivalled}]
     n 1: model of excellence or perfection of a kind; one having no
          equal [syn: {ideal}, {paragon}, {saint}, {apotheosis}, {nonesuch},
           {nonsuch}]
     2: colored beads of sugar used as a topping on e.g. candies and
        cookies
     3: a flat disk of chocolate covered with beads of colored sugar

Source : Free On-Line Dictionary of Computing

Nonpareil
     
        One of five pedagogical languages based on {Markov
        algorithm}s, used in ["Nonpareil, a Machine Level Machine
        Independent Language for the Study of Semantics", B. Higman,
        ULICS Intl Report No ICSI 170, U London (1968)].  The others
        were {Brilliant}, {Diamond}, {Pearl} and {Ruby}.